1. Field of the Invention
This invention relates generally to optical wireless communication links, and more particularly, to a system and method of polarizing the transmitted beam and detecting the polarization at the receiver in order to measure positioning accuracy.
2. Description of the Prior Art
An optical wireless link system consists of two stations (OWLs): Each of which contains an optical transmitter and an optical receiver. The transmitter is able to change the direction of its transmitted beam by known amounts of angular displacement. The receiver senses the position of the incident beam relative to the local data detector and sends position correction information back to the transmitter. This feedback is used by a servo control loop to position the transmitted beam on the receiver of the remote station.
A typical remote feedback sensor which is distinct from the data detector (for example quad position detectors surrounding the data detector) used in a micro-electro-mechanical (MEM) mirror has inherent non-linearities. These non-linearities adversely affect the mirror movement control system. Such non-linearities change the apparent gain of the control system limiting the tracking performance. Further, there is considerable cost associated with the quad position detectors. The cost of the OWLs must be as low as possible for a mass market device.
In view of the foregoing, it would be both desirable and advantageous in the optical wireless communication art to provide a technique that eliminates the nonlinearities associated with the remote feedback sensor used in an optical wireless link (OWL) unit. It would also be advantageous if the technique could be implemented at substantially less cost than that generally associated with quad position detectors.